The line control device brings great convenience to user terminals, such as a smart phone, a tablet computer, and so on. For example, a line control device applied in an earphone line of a user terminal can be used to control functions of the user terminal, such as answering or rejecting a call, switching songs, adjusting volume, and so on. However, most existing line control devices are button-type control devices made of hard material, or touch-type control devices with touch panels arranged at hard material. To control functions of the user terminals through these line control devices, specific button combinations or touch gestures are required. When the line control device is out of sight of the user, touch operations are required to locate the corresponding button and the touch panel. Thus, the operation efficiency of the existing line control device is limited. In addition, the existing line control device has too few operation gestures to achieve a richer function control.